Method and Structure for Preventing Screw From Loosening and Method of Manufacturing Male Screw

ABSTRACT

Prior to engaging a male screw formed on the outer circumference of a second member with a female screw formed on the inner circumference of a hole in a first member, protruding parts which protrude outward in the radial direction and are positioned at one end side of the male screw in the axial direction are formed in a plurality of regions which are separated from each other in the circumferential direction on the outer circumference of the second member on which the male screw is formed. The male screw is then engaged with the female screw from the other end side of the male screw in the axial direction. The torque required to rotate the male screw engaged with the female screw in the loosening direction is set so as to be greater in a state where the protruding parts are interposed between the male screw and the female screw than in a state where the protruding parts are not so interposed.

BACKGROUND OF THE INVENTION

The present invention relates to a method and structure for preventingthe loosening of a male screw which is engaged with a female screw, anda method for manufacturing this male screw.

In a rack and pinion type steering apparatus equipped with a rack matingwith a pinion which is rotated by steering operation, a female screw isformed on the inner circumference of a hole formed in a housing whichcovers the rack, the opening of the hole is closed by engaging a malescrew formed on the outer circumference of a closing member with thefemale screw, and an elastic member which presses a rack supportingmember inserted into the hole against the rack is sandwiched between therack supporting member and the closing member. The gap between the racksupporting member and the closing member is adjusted by adjusting theamount by which the male screw is engaged with the female screw, so thatfluctuation in the amount of mating between the rack and the pinioncaused by bending of the rack and others is prevented, thus making itpossible to achieve smoother mating.

Conventionally, in order to prevent loosening of the male screw formedon the abovementioned closing member, a lock nut is engaged with thismale screw (Patent Document 1).

Patent Document 1: Japanese Patent Application Laid-open No. 1979-138239SUMMARY OF THE INVENTION

In the prior art, since the lock nut is necessary, the number of partsis increased. Furthermore, the male screw rotates with respect to thefemale screw when the lock nut is engaged, so that the gap between therack supporting member and closing member fluctuates. As a result, sinceit is necessary to readjust this gap, the productivity drops.Furthermore, since a temporary assembly process in which the lock nut isprovisionally engaged with the male screw is required prior to theprocess in which the male screw is engaged with the female screw, theworking efficiency is poor. It is an object of the present invention toprovide a method and structure for preventing screw loosening and amethod for manufacturing a male screw that can solve such problems.

In the method of the present invention for preventing screw loosening,prior to engaging a male screw formed on the outer circumference of asecond member with a female screw formed on the inner circumference of ahole in a first member, protruding parts which protrude outward in theradial direction and are positioned at one end side of the male screw inthe axial direction are formed in a plurality of regions which areseparated from each other in the circumferential direction on the outercircumference of the second member on which the male screw is formed,the male screw is then engaged with the female screw from the other endside of the male screw in the axial direction, and the torque requiredto rotate the male screw engaged with the female screw in the looseningdirection is set so as to be greater in a state where the protrudingparts are interposed between the male screw and the female screw than ina state where the protruding parts are not interposed between the malescrew and the female screw.

The structure of the present invention for preventing screw looseningcomprises a first member which has a hole, a female screw which isformed on the inner circumference of the hole, a second member which hasan outer circumference, a male screw which is formed on the outercircumference of the second member, and a recessed part which is formedin the second member so as to be positioned to the inside of the malescrew in the radial direction, wherein plastic deformation parts whichare plastically deformed outward in the radial direction are formed in aplurality of regions which are separated from each other in thecircumferential direction on the inner circumference of the recessedpart, protruding parts which are protruded outward in the radialdirection by the formation of the plastic deformation parts are formedin a plurality of regions which are separated from each other in thecircumferential direction on the outer circumference of the secondmember on which the male screw is formed, the protruding parts arepositioned at one end side of the male screw in the axial direction, andthe torque required to rotate the male screw engaged with the femalescrew in the loosening direction is set so as to be greater in a statewhere the protruding parts are interposed between the male screw and thefemale screw than in a state where the protruding parts are notinterposed between the male screw and the female screw.

According to the method of the present invention, no protruding partsare interposed between the male screw and the female screw in theinitial stage of the operation for engaging the male screw with thefemale screw, so that this operation can be easily initiated. Sinceprotruding parts are subsequently interposed between the male screw andthe female screw, the friction between the male screw and the femalescrew can be increased so that loosening of the male screw with respectto the female screw is restricted. Furthermore, since loosening of themale screw with respect to the female screw can be restricted withoutusing a lock nut, the number of parts can be reduced, so that theproductivity and working efficiency can be improved. In addition, themale screw can be loosened with respect to the female screw if necessaryby applying torque exceeding the set value on the male screw.Inadvertent loosening of the male screw with respect to the female screwcan be prevented by controlling the torque required to loosen the malescrew with respect to the female screw. The method of the presentinvention can be realized using the structure of the present invention.

It is desirable that the torque required to rotate the male screwengaged with the female screw in the loosening direction is set so as tobe equal to or greater than 10 Newton-meter in a state where theprotruding parts are interposed between the male screw and the femalescrew, and is set so as to be equal to or less than 1 Newton-meter in astate where the protruding parts are not interposed between the malescrew and the female screw. As a result, the male screw can be easilyengaged with the female screw, and inadvertent loosening of the malescrew with respect to the female screw can be securely prevented.

It is desirable that the second member is pressed against a pressurereceiving part which is to be fixed to the first member, at the otherend of the male screw engaged with the female screw via the protrudingparts, and that the torque required to rotate the male screw engagedwith the female screw in the loosening direction is set so as to beequal to or greater than 3 Newton-meter in a state where the protrudingparts are interposed between the male screw and the female screw, and isset so as to be equal to or less than 1 Newton-meter in a state wherethe protruding parts are not interposed between the male screw and thefemale screw. As a result, the male screw can be easily engaged with thefemale screw, and the friction between the male screw and the femalescrew can be increased by the reaction force that acts on the other endof the male screw, so that inadvertent loosening of the male screw withrespect to the female screw can be securely prevented.

It is desirable that the first member is constituted by a housing whichcovers a rack mating with a pinion, which is caused to rotate bysteering operation, that an elastic member is provided so as to applyelastic force for pressing a rack supporting member inserted into thehole against the rack, that the second member is constituted by aclosing member which closes the opening of the hole, and that theelastic member is sandwiched between the rack supporting member and theclosing member. As a result, the present invention can be applied to arack and pinion type steering apparatus, the male screw can be loosenedwith respect to the female screw if necessary by applying torque whichexceeds a set torque on the male screw, and the adjustment of the gapbetween the rack supporting member and the closing member can beperformed with good efficiency.

In the method of the present invention for manufacturing the male screwin the structure for preventing screw loosening, three pressing partsare integrally disposed so as to be inclined with respect to the axis ofthe male screw and separated from each other in the circumferentialdirection of the male screw with facing the circumferential edge of theopening of the recessed part, these three pressing parts as an integralunit are then moved integrally in the axial direction of the male screwrelatively to the second member, and the plastic deformation parts areformed by pressing the respective pressing parts against thecircumferential edge of the opening of the recessed part. In the presentinvention, since the number of pressing parts which are pressed againstthe circumferential edge of the opening in the second member is three,the respective pressing parts can be uniformly pressed against thecircumferential edge of the opening of the recessed part. As a result,the amounts of plastic deformation in the respective plastic deformationparts can be made uniform, so that the amounts of protrusion of therespective protruding parts can be made uniform; therefore, the torquerequired to loosen the male screw can be accurately set, so thatinadvertent loosening of the male screw with respect to the female screwcan be securely prevented.

The present invention makes it possible to provide a method andstructure for preventing screw loosening in which the number of partscan be reduced, the productivity can be improved, and the workingefficiency can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 A longitudinal sectional view of an essential part of a rack andpinion type steering apparatus in an embodiment of the present invention

FIG. 2 A partially sectional front view of an essential part of the rackand pinion type steering apparatus in the embodiment of the presentinvention

FIG. 3 A front view of the closing member in the embodiment of thepresent invention

FIG. 4A A plan view of the pressing part in the embodiment of thepresent invention

FIG. 4B A side view of the pressing part in the embodiment of thepresent invention

FIG. 5A A diagram showing the state prior to the formation of theplastic deformation parts by the pressing parts in the embodiment of thepresent invention

FIG. 5B A diagram showing the state following the formation of theplastic deformation parts by the pressing parts in the embodiment of thepresent invention

FIG. 6A A diagram showing the initial state of the operation forengaging the male screw with the female screw in the embodiment of thepresent invention

FIG. 6B A diagram showing the state after the male screw is engaged withthe female screw in the embodiment of the present invention

FIG. 7 A longitudinal sectional view of an essential part of a rack andpinion type steering apparatus in a modification of the presentinvention

DETAILED DESCRIPTION OF THE INVENTION

The rack and pinion type steering apparatus 1 shown in FIGS. 1 and 2comprises an input shaft 2 which is connected to the steering wheel (notshown in the figures), a helical pinion 3 which is formed on the outercircumference of the input shaft 2, a helical rack 4 which mates withthe pinion 3 via teeth 4 a, and a housing 5 which covers the pinion 3and rack 4. The first member of the present invention is constituted bythe housing 5. The housing 5 supports the input shaft 2 via a ballbearing 6 and a needle bearing 7. The inner race 6 a of the bearing 6 issandwiched by a step 2 a of the input shaft 2 and a ring 8 attached tothe input shaft 2, and the outer race 6 b is sandwiched by a step 5 ainside a shaft retaining hole 5′ formed in the housing 5 and a snap ring9 attached to the housing 5. A seal 10 is disposed between the inputshaft 2 and the housing 5. The rack 4 is moved in the lateral directionof the vehicle by the rotation of the pinion 3 caused by steeringoperation, so that the steering angle of the wheels connected to bothends of the rack 4 via link mechanisms (not shown in the figures)varies.

The housing 5 has a retaining part 5″ extending from the position atwhich the pinion 3 mates with the rack 4 to a direction perpendicular tothe longitudinal direction of the rack 4. A hole 15 is formed in theretaining part 5″. A rack supporting member 16 is inserted into the hole15 so as to be capable of reciprocating in a direction perpendicular tothe longitudinal direction of the rack 4. The opening of the hole 15 isclosed by a closing member 18. The second member of the presentinvention is constituted by the closing member 18. A male screw 18A isformed on the outer circumference of the closing member 18, and the malescrew 18A is engaged with a female screw 15A formed on the innercircumference of the hole 15, so that the opening of the hole 15 isclosed by the closing member 18. A recessed part 18 a is formed in oneend of the closing member 18 so as to be positioned to the inside of themale screw 18A in the radial direction, so that the closing member 18has the shape of a tube having a bottom. The opening side of the innercircumference of the recessed part 18 a is formed as a tool engagingpart 18 b conforming to the shape of a polygonal column, the bottom side18 c of the recessed part 18 a is formed with a shape conforming to acircular conical surface. The male screw 18A can be engaged with thefemale screw 15A or loosened with respect to the female screw 15A byinserting a tool (not shown in the figures) such as a wrench or the likewhich has an outer circumference conforming to the tool engaging part 18b, and rotating the closing member 18. Furthermore, a sealing ring 19 ais disposed between the closing member 18 and the housing 5.

One end of the rack supporting member 16 faces the other end of theclosing member 18. The other end of the rack supporting member 16supports the back surface of the rack 4 via a sheet 17. An elasticmember 20 constituted by a compression coil spring is inserted into ahole 16 a formed in one end of the rack supporting member 16. Theelastic member 20 is compressed by being sandwiched between the racksupporting member 16 and the closing member 18, so that elastic force isapplied so as to press the rack supporting member 16 against the rack 4.As a result, smooth engagement between the rack 4 and the pinion 3 isensured by the movement of the rack supporting member 16. The amount ofmovement of the rack supporting member 16 due to the bending of the rack4 and others is corrected by the adjustment of the gap S between one endof the rack supporting member 16 and the other end of the closing member18, so that the engagement between the rack 4 and pinion 3 is ensured.This adjustment of the gap S is performed by adjusting the amount bywhich the male screw 18A is engaged with the female screw 15A.Furthermore, a sealing ring 19 b is disposed between the rack supportingmember 16 and the housing 5.

As is shown in FIG. 3, plastic deformation parts 30 which areplastically deformed outward in the radial direction are formed in aplurality of regions (three regions in the present embodiment) which areseparated from each other in the circumferential direction on the innercircumference of the recessed part 18 a of the closing member 18. Eachof the plastic deformation parts 30 is formed by plastically deforming aportion of the circumferential edge 18 a′ of the opening of the recessedpart 18 a. Protruding parts 40 which are protruded outward in the radialdirection by the formation of the plastic deformation parts 30 areformed in a plurality of regions (three regions in the presentembodiment) which are separated from each other in the circumferentialdirection on the outer circumference of the closing member 18 on whichthe male screw 18A is formed. The respective protruding parts 40 arepositioned at one end side of the male screw 18A in the axial direction(toward the outside of the housing 5), and the male screw 18A is engagedwith the female screw 15A from the other end side of the male screw 18Ain the axial direction. As a result, the torque required to rotate themale screw 18A engaged with the female screw 15A in the looseningdirection is set so as to be greater in a sate where the protrudingparts 40 are interposed between the male screw 18A and the female screw15A than in a state where these protruding parts 40 are not sointerposed. Here, since the amount of protrusion of the protruding parts40 is so small (e.g., 0.1 mm or less) that this amount of protrusion isdifficult to distinguish with the naked eye, the outer circumference ofthe male screw 18A is shown as conforming to a circle in the figures.

In the present embodiment, the male screw 18A is formed by, for example,rolling, and then the plastic deformation parts 30 are formed by thepressing tool 50 shown in FIGS. 4A and 4B. The pressing tool 50 has amain body 51 in the shape of a hexagonal nut, and three blades 52protruding from the outer circumference of the main body 51. Therespective blades 52 have the same configuration, and are disposed atequal intervals in the circumferential direction of the main body 51. Apressing part 52 a in the shape of an edge is formed on one end of eachblade 52. Each of the pressing parts 52 a is inclined with respect tothe axial direction of the main body 51 (the vertical direction in FIG.4B) so as to tend from one end to the other end of the main body 51 asit is distanced from the outer circumference of the main body 51.

For example, one of the pressing tool 50 and the closing member 18 isattached to the ram of a pressing device, and the other is fastened to atable or the like. As a result, as shown in FIG. 5A, by making the axisof the main body 51 coincide with the axis of the closing member 18, thethree pressing parts 52 a can be integrally disposed so as to beinclined with respect to the axis of the male screw 18A and separatedfrom each other in the circumferential direction of the male screw 18Awith facing the circumferential edge 18 a′ of the opening of therecessed part 18 a. Subsequently, the closing member 18 and the pressingtool 50 are moved relatively in the axial direction of the male screw18A by the pressing device, so that the three pressing parts 52 a as anintegral unit are moved in the axial direction of the male screw 18Arelatively to the closing member 18 as shown in FIG. 5B. As a result,the respective pressing parts 52 a are pressed against thecircumferential edge 18 a′ of the opening of the recessed part 18 a, sothat plastic deformation parts 30 which are plastically deformed outwardin the radial direction are formed in three regions which are separatedfrom each other in the circumferential direction on the innercircumference of the recessed part 18 a. As a result of the formation ofthe respective plastic deformation parts 30, protruding parts 40 whichare protruded outward in the radial direction are formed in threeregions which are separated from each other in the circumferentialdirection on the outer circumference of the closing member 18 on whichthe male screw 18A is formed.

In the present embodiment, it is desirable that the torque required torotate the male screw 18A engaged with the female screw 15A in theloosening direction is set equal to or greater than 10 Newton-meter,preferably equal to or greater than 25 Newton-meter and equal to or lessthan 50 Newton-meter, in a state where the protruding parts 40 areinterposed between the male screw 18A and the female screw 15A, and thatthis torque is set equal to or less than 1 Newton-meter in a state wherethe protruding parts 40 are not interposed between the male screw 18Aand the female screw 15A. Since the protruding parts 40 are formed bythe formation of the plastic deformation parts 30 which are formed bypressing the pressing parts 52 a against the circumferential edge 18 a′of the opening of the recessed part 18 a in the axial direction, theprotruding parts 40 can be formed, after determining the value ofpressing force or the amount of pressing in the axial direction bypreliminary experiment so that the torque required to rotate the malescrew 18A engaged with the female screw 15A in the loosening directionbecomes a set torque. It is desirable to reduce the manufacturingtolerance of the male screw 18A and the female screw 15A prior toforming the protruding parts 40 for accurately setting this set torqueat a desired value. For example, the precision of the male screw 18A isset at a precision higher than 4 h (ISO), and the precision of thefemale screw 15A is set at a precision higher than 4 H (ISO).Furthermore, in the initial stage of the operation for engaging the malescrew 18A with the female screw 15A, torque exceeding 50 Newton-meter,e.g., approximately 75 Newton-meter, is applied in the tighteningdirection, so that the rack 4 is pressed against the pinion 3 by theclosing member 18 via the rack supporting member 16. In this state, thepinion 3 is rotated so that members, which contact with each other, suchas the rack 4 and pinion 3, and the rack 4 and rack supporting member 16work in with each other in a good fit condition. It is desirable thattorque oriented in the loosening direction of the male screw 18Asubsequently applied in order to adjust the gap S.

In the abovementioned construction, prior to engaging the male screw 18Awith the female screw 15A, respective protruding parts 40 positioned atone end side of the male screw in the axial direction are formed on theouter circumference of the closing member 18 on which the male screw 18Ais formed, and then the male screw 18A is engaged with the female screw15A from the other end side of the male screw 18A in the axialdirection. The torque required to rotate the male screw 18A engaged withthe female screw 15A in the loosening direction is set so as to begreater in a state where the protruding parts 40 are interposed betweenthe male screw 18A and female screw 15A than in a state where theprotruding parts 40 are not so interposed. As a result, as shown in FIG.6A, since the protruding parts 40 are not interposed between the malescrew 18A and female screw 15A in the initial stage of the operation forengaging the male screw 18A with the female screw 15A, so that thisoperation can be easily initiated. Subsequently, when one end side ofthe male screw 18A is engaged with the female screw 15A as shown in FIG.6B, the protruding parts 40 are interposed between the male screw 18Aand the female screw 15A; therefore, the friction between the male screw18A and the female screw 15A is increased, so that the loosening of themale screw 18A with respect to the female screw 15A is restricted. Inparticular, since the torque required to rotate the male screw 18Aengaged with the female screw 15A in the loosening direction is set at10 Newton-meter or greater in a state where the protruding parts 40 areinterposed between the male screw 18A and the female screw 15A, and isset at 1 Newton-meter or less in a state where the protruding parts arenot interposed between the male screw 18A and female screw 15A, theengaging of the male screw 18A with the female screw 15A can be easilyperformed, and the inadvertent loosening of the male screw 18A withrespect to the female screw 15A can be securely prevented. Furthermore,since the loosening of the male screw 18A with respect to the femalescrew 15A can be restricted without using a lock nut, the number ofparts can be reduced, the productivity can be improved, and the workingefficiency can be improved. Furthermore, the male screw 18A can beloosened with respect to the female screw 15A if necessary by applyingtorque exceeding the set value. Accordingly, the efficiency of theadjustment operation of the gap S between the rack supporting member 16and the closing member 18 can be improved. By controlling the torque toloosen the male screw 18A with respect to the female screw 1.5A, it ispossible to prevent inadvertent loosening of the male screw 18A withrespect to the female screw 15A. Furthermore, when the plasticdeformation parts 30 are formed by means of the pressing tool 50, sincethe number of pressing parts 52 a pressed against the circumferentialedge 18 a′ of the opening of the recessed part 18 a is three, therespective pressing parts 52 a can be uniformly pressed against thecircumferential edge 18 a′ of the opening of the recessed part 18 a. Asa result, the amount of plastic deformation in the respective plasticdeformation parts 30 can be made uniform, so that the amount ofprotrusion of the respective protruding parts 40 can be made uniform;therefore, the torque required to loosen the closing member 18 can beaccurately set, so that inadvertent loosening of the male screw 18A withrespect to the female screw 15A can be securely prevented.

Instead of the snap ring 9 for fastening the outer race 6 b in theabovementioned embodiment, an annular member 70 illustrated in FIG. 7can be used as the second member of the present invention. Specifically,a male screw 70A engaged with a female screw 5A formed on the innercircumference of the shaft retaining hole 5′ of the housing 5 is formedon the outer circumference of the annular member 70. The hole defined bythe inner circumference of the annular member 70 serves as the recessedpart 70 a of the present invention. Plastic deformation parts 80plastically deformed outward in the radial direction are formed in threeregions of the circumferential edge 70 a′ of the opening of the recessedpart 70 in the same manner as in the abovementioned embodiment. As aresult, at one end side of the male screw 70A in the axial direction,protruding parts 90 which protrude outward in the radial direction areformed on the outer circumference of the annular member 70 on which themale screw 70A is formed, in the same manner as in the abovementionedembodiment. The annular member 70 is pressed against the outer race 6 b(pressure receiving part) which is to be fixed to the housing 5, at theother end of the male screw 70A engaged with the female screw 5A via theprotruding parts. In this case, it is desirable that the torque requiredto rotate the male screw 70A engaged with the female screw 5A is set soas to be equal to or greater than 3 Newton-meter in a state where theprotruding parts 90 are interposed between the male screw 70A and thefemale screw 5A, and that it is set so as to be equal to or less than 1Newton-meter in a state where the protruding parts 90 are not interposedbetween the male screw 70A and the female screw 5A. As a result, theengaging of the male screw 70A with the female screw 5A can be easilyperformed, and since the friction between the male screw 70A and thefemale screw 5A can be increased by the reaction force which acts on theother end of the male screw 70A from the outer race 6 b, the inadvertentloosening of the male screw 70A with respect to the female screw 5A canbe securely prevented. The remaining construction is the same as in theabovementioned embodiment.

The present invention is not limited to the abovementioned embodiments.For example, the present invention is not limited to application to rackand pinion type steering apparatuses, but can be applied to anystructure in which a male screw formed on the outer circumference of asecond member is engaged with a female screw formed on the innercircumference of a hole in a first member.

1. A method for preventing screw loosening, comprising prior to engaginga male screw formed on the outer circumference of a second member with afemale screw formed on the inner circumference of a hole in a firstmember, forming protruding parts which protrude outward in the radialdirection and are positioned at one end side of said male screw in theaxial direction, said protruding parts being formed in a plurality ofregions which are separated from each other in the circumferentialdirection on the outer circumference of said second member on which saidmale screw is formed, then engaging said male screw with said femalescrew from the other end side of said male screw in the axial direction,and setting torque required to rotate said male screw engaged with saidfemale screw in the loosening direction so as to be greater in a statewhere said protruding parts are interposed between said male screw andsaid female screw than in a state where said protruding parts are notinterposed between said male screw and said female screw.
 2. A structurefor preventing screw loosening comprising: a first member which has ahole; a female screw which is formed on the inner circumference of saidhole; a second member which has an outer circumference; a male screwwhich is formed on the outer circumference of said second member;wherein a recessed part which is formed in said second member so as tobe positioned to the inside of said male screw in the radial direction,wherein plastic deformation parts which are plastically deformed outwardin the radial direction are formed in a plurality of regions which areseparated from each other in the circumferential direction on the innercircumference of said recessed part, protruding parts which areprotruded outward in the radial direction by the formation of saidplastic deformation parts are formed in a plurality of regions which areseparated from each other in the circumferential direction on the outercircumference of said second member on which said male screw is formed,said protruding parts are positioned at one end side of said male screwin the axial direction, and torque required to rotate said male screwengaged with said female screw in the loosening direction is set so asto be greater in a state where said protruding parts are interposedbetween said male screw and said female screw than in a state where saidprotruding parts are not interposed between said male screw and saidfemale screw.
 3. The structure for preventing screw loosening accordingto claim 2, wherein the torque required to rotate said male screwengaged with said female screw in the loosening direction is set so asto be equal to or greater than 10 Newton-meter in a state where saidprotruding parts are interposed between said male screw and said femalescrew, and is set so as to be equal to or less than 1 Newton-meter in astate where said protruding parts are not interposed between said malescrew and said female screw.
 4. The structure for preventing screwloosening according to claim 2, wherein said second member is pressedagainst a pressure receiving part which is to be fixed to said firstmember, at the other end of said male screw engaged with said femalescrew via said protruding parts, and the torque required to rotate saidmale screw engaged with said female screw in the loosening direction isset so as to be equal to or greater than 3 Newton-meter in a state wheresaid protruding parts are interposed between said male screw and saidfemale screw, and is set so as to be equal to or less than 1Newton-meter in a state where said protruding parts are not interposedbetween said male screw and said female screw.
 5. The structure forpreventing screw loosening according to any of claims 2 through 4,wherein said first member is constituted by a housing which covers arack mating with a pinion, which is caused to rotate by steeringoperation, an elastic member is provided so as to apply elastic forcefor pressing a rack supporting member inserted into said hole againstsaid rack, said second member is constituted by a closing member whichcloses the opening of said hole, and said elastic member is sandwichedbetween said rack supporting member and said closing member.
 6. A methodfor manufacturing a male screw in the structure for preventing screwloosening according to any of claims 2 through 4, wherein three pressingparts are integrally disposed so as to be inclined with respect to theaxis of the male screw and separated from each other in thecircumferential direction of the male screw with facing thecircumferential edge of the opening of the recessed part, said threepressing parts as an integral unit are then moved in the axial directionof said male screw relatively to said second member, and said plasticdeformation parts are formed by pressing the respective pressing partsagainst the circumferential edge of the opening of said recessed part.